Influence of iron deficiency anaemia on haemoglobin A2 levels: possible consequences for beta-thalassaemia screening

Iron deficiency modulates the synthesis of HbA2, resulting in reduced HbA2 levels in patients with iron deficiency anaemia. The diagnosis heterozygous beta-thalassaemia is based on a raised HbA2 level. Patients with beta-thalassaemia and concomitant iron deficiency can show normal HbA2 levels. It is of clinical importance to know the quantitative effect of iron-deficient erythropoiesis on the levels of HbA2 in order to be able to determine which iron-deficient patients with normal HbA2 levels have to be retested after iron therapy in thalassaemia screening programmes. In this study, HbA2 levels in 150 patients with iron-deficiency anaemia and 71 healthy controls have been measured. A linear correlation is found in the patient group between HbA2 and Hb, HbA2 and MCV, and HbA2 and erythrocyte zinc protoporphyrin (ZPP). In future studies, the correlation between HbA2 and erythrocyte parameters in patients with heterozygous beta-thalassaemia and concomitant iron deficiency has to be examined. We recommend that ZPP be measured in these studies too, as ZPP levels may be a better indicator of concomitant iron deficiency than Hb or MCV in thalassaemic patients.